Cause of disorder?
The window was left open and she was raped.

Disorder?
Anxiety disorder. OCD. PTSD (Post-traumatic stress disorder)

Treatment?
Make Nancy stay and sleep in the room with close friends and parents => take locks away => take people away one by one as Nancy gets used to being in an unlocked room
=> let her sleep alone with the doors and windows locked
Get a pet => will make her feel more secure
Receive counselling
Interact with parents and female friends. ( maybe live with the parents for a while or get a female friend roommate.)
Security systems (electronically detect whether doors are open. Call police when forced to be opened)

Through this systematic desensitization, Nancy will overcome her anxiety of being raped.